How can I get my 4g phone to reliably and seamlessly talk to my network extender?

Question

I moved a few months ago, and ever since I've had major problems with dropped calls on my phone.
Before, I was on the inside of a large concrete apartment building, and I had the 3g network extender. Because I was near the center of the building, despite the courtyard in the middle, I had no problem connecting to the 3g extender, as there was no meaningful competing signal.
Now, I'm across the street, but on the outside of the building. Calls were able to connect sometimes from within the apartment (without the extender) because there is some cellular coverage. However, we would occasionally drop calls on all three VZW cell phones in the apartment, I reactivated the network extender. This has helped the two other lines (a Stratosphere II/Galaxy Nexus and a Galaxy S4) immensely. However, my phone will consistently drop calls just a few seconds in - excluding the Lumia, which doesn't hit the network extender and therefore seems to drop slightly less often since there is no handoff. I typically see 1-2 bars of signal.
A few of the troubleshooting steps I've tried:
I have gotten a brand new SIM from a VZW corporate store
I hate tried multiple phones - Galaxy S3, Nexus (the same one that another household user has not had any problems with), and a Lumia 822
I have ensured that I'm on the network extender via #48 - I get on the extender on all phones except the Lumia 822, which doesn't drop calls quite as often. This is even the case when I'm connected to LTE on the Android phones; this makes sense, since the extender is 3g/1x only, and all voice calls are over 1x.
I have tried multiple distances between the phone and network extender - both very close (within 3 feet) and farther (15 feet + wall)
I have tried my phone(s) without cases, and typically use a thin TPU rubber case  on the galaxy S3.
I hate tried factory resets on all three phones.
I have ensured that my phone number is on the network extender access list.
If I disable LTE (some phones are easier than others; for example the GS3 makes this rather difficult. The menu under Settings > More Settings > Mobile Networks < Network Mode) offers three options: Global, LTE/CDMA, and GSM/UMTS. However, third-party apps can adjust this; for example, "Advanced Signal Status" can (via Addition Info > Device Information). When I set my phone to CDMA only there, I get a solid connection. #48 still tells me I'm on the network extender, and I have 5 bars of signal. I use another app, SignalCheck Lite, to give me solid signal readings.
Signal Measurements:
Galaxy S3, CDMA only (via 3p app), <3 feet from extender
5 Bars, connected to wifi and non-LTE signal, will not drop calls
1xRTT: -61 dBm
EvDo: -72 dBm, SNR 8 dB
LTE: No connection
Wifi: -64 dBm
Galaxy S3, normal LTE/CDMA mode, <3 feet from extender
1 Bar, connected to wifi and presumably LTTE signal, will drop calls FREQUENTLY
1xRTT: -66 dBm
EvDo: No longer shown in app; eHRPD is shown with no connection
LTE -117 dBm, SNR 7dB
Wifi: -67 dBm
Given that the 1xRTT signal is reasonably strong in both cases, my suspicion is that a handoff is occurring incorrectly. It's prioritizing the LTE base station over the extender, despite the large signal discrepancy. My understanding is that a handoff can occur from extender to VZW tower, but not the other way around - so one it has transferred over, it will inevitably drop, often just a few seconds into the call.
However, the 'CDMA only' is not a good solution. Along with not being something normally in the device's settings, this is a major inconvenience - even if it were the settings screen, that's 5+ taps every time I enter or exit my apartment. (Nor can this be automated with a tool like Tasker.)

Answer 1

AdaS_VZW,
I'm not sure if the area has been surveyed; it's a large group of apartment buildings about a within a couple miles of Dulles International Airport in Northern Virginia, so I would imagine that it probably has, but I'm not sure. How would I find out?
I understand that the Network Extender does not support LTE connections (I know there are two models, the 1x-only and 3g, both made by Samsung - I have the 3g model, SCS-2U01). I know that it can support a 3G data connection, but that should be irrelevant - I'm always connected to my wifi network in my apartment.
What's particularly vexing, however, is that both a Galaxy S4 and Galaxy Nexus in my apartment (the other lines on my account) do not seem to have this issue. While I haven't done so with the S4, the Nexus exhibits this problem when my SIM is in it - and again, this is a fresh SIM from just a few weeks ago.
I'm currently trying to disable Mobile Data when in the apartment to see if that will make it more stable. I'll post in a day or two with results from that.
Shawn